Carburetor



CARBURE'I'OR Filed Oct. 13, 1957 INVEN TOR gm-um Q. MOCK nteed lott 9onnmmn'ron' Frank 0. Mock, South Bend, llnd., assignor to BendixProducts Corporation,

South Bend,

Ind., a corporation of Indiana Application October 13, 1937, Serial No.168,690

4 Claims.

This invention relates to carburetors and more particularly to means forpreventing fuel from boiling out of the main nozzle of the carburetor.This application is a continuation in part of my copending applicationSerial No. 47,930, filed November 2, 1935.

The phenomenon commonly known as percolation occurs when the fuel withinthe main nozzle vaporizes under the influence of heat from the engine,particularly when the engine is stopped after having been operated, thevapor escaping from the nozzle outlet in intermittent bubbles whichcarry with them liquid fuel which, in a downdraft carburetor, passesinto the intake manifold and engine cylinders, where it hinders thestarting and operation of the engine.

A major portion of the heat which causes such percolation flows byconduction from the intake manifold through the throttle body section ofthe carburetor to the metal adjacent the main nozzle.

An object of the present invention is to impede the flow of heat fromthe intake manifold to the main nozzle by providing a region of low heatconductivity through which the heat must pass in order to reach thenozzle.

A further object of the invention is to provide means for transferringto the'fuel in the carburetor fuel reservoir the heat which does reachthe vicinity of the main nozzle.

A further object of the invention is to cool the main nozzle bysurrounding it and its associated elements with a body of fuel which isin free communication with the'fuel contained in the float chamber ofthe carburetor. 4

Further obiects and advantages of the invention will be apparent fromthe following descriptlon, considered in connection with theaccompanying drawing, which is submitted for purposes of illustrationonly and not intended to define the scope of the invention, referencebeing had for that purpose to the appended claims.

Figure l is a vertical section through a carburetor embodying theinvention;

Figure 2 is a fragmentary sectional view taken on the line 2- 3 ofFigure 1;

Figure 3 is a similar view taken on line 3-3 of Figure l.

Referring more particularly to Figure 1, there is shown a carburetorhaving an airhorn section a main body section it, and athrottle bodysection 2%. The airhorn'sectlon 28 forms an air inlet passage 2% toadmit air controlled by an unbalanced cholre valve 2t mounted on a chokeshaft m. rotatably mounted in the airhorn section W. e main body section22 is provided with a primary venturi 32, projected into the mid-portionof an induction passage 34 formed by the three sections of thecarburetor mentioned above. A fuel reservoir 36 is adapted to maintainliquid fuel therein at the level indicated at L-L in Figure 1, and tosupply the same to the primary venturi 32 by means of a fuel dischargenozzle 38, communicating with the fuel reservoir 36 and projectingthrough a fin 40 supporting the primary venturi 32. The primary venturi32 thus operates to supply a rich mixture of fuel and air into theinduction passage 34 immediately posterior to the restricted section ofa secondary venturi 42 formed integral with the fuel reservoir section22. The rich mixture supplied by the primary venturi is diluted by asuitable quantity of air admitted through the secondary venturi 42 toform a combustible mixture for the operation of the engine to which thecarburetor is attached. The combustible mixture thus formed is passed tothe engine by way of the throttle body section 2t having a throttlevalve M fixed to a throttle shaft l6 rotatably mounted in the walls ofthe throttle body section M. v

The main fuel nozzle 38 is positioned in an integral boss t8 whichextends into a chamber 49 forming the lower section or the fuelreservoir 36 and closed by a threaded plug 5|. The boss tt is ofgenerally cylindrical shape and is practically surrounded by a cored-outrecess 58 which receives fuel from the fuel reservoir 36 which ab sorbsand dissipates heat from the boss.

Fins may be provided on boss it, as shown, if it is desirable toincrease the heat dissipating capacity of the boss. The fins may be castintegral with the boss or, to facilitate die-casting the main bodysection 22, may be provided on a separate piece adapted to be pressed orthreaded into the boss. A baflie 51! projects downwardly in the recess58 and extends longitudinally of the boss t8 to a point beyond theentrance to the nozzle lit. The baiiie is arcuately shaped and whollyspaced. both from the boss t8 and from the bottom'of the reservoir 36 toprevent vapor generated in the bottom of recess 5E) and reservoir 36from being drawn-into the fuel nozzle 38.

In order to impede the flow of heat upwardly from the intake manifold, athick gasket 52 of heat insulating material is interposed between thethrottle body section 26 and the main body section 22, and themetakto-metal contact between the two sections is minimized by limitingthe overlap between venturi t2 and the throttle body section to a narrowannulus, as indicated at St. The main body section is also cored outtoform an annular recess 56 which forms a dead-air heat-insulating spacebetween the venturi 42 and the remainder of the main body section. Heatcan travel upwardly to the main nozzle only by passing through arelatively thin flange or neck 58 lying between recess 50 and theinduction passage 34, and what heat reaches the boss 48 surrounding themain nozzle is transferred to the fuel in the chamber 49, usually beforethe temperature reaches the boiling point of the fuel.

If boiling occurs in the fuel in chamber 50, the vapors escape upwardlythrough grooves 60 which extend vertically at each side of the boss 48and have free communication with the float cham- -ber36.

The fuel system of the carburetor comprises a fuel well 62 communicatingwith the interior of the main nozzle through a series of air-bleed holes64. An idling fuel passage 66 extends vertically from the lower portionof the nozzle 38 through an idling tube 68 and thence through passagesnot shown to a nozzle adjacent the throttle. The arrangement shown issuch that even if, under extreme circumstances, a degree of boilingoccurs in the main nozzle the supply of idling fuel, which is drawn fromthe bottom of the nozzle, is not interrupted,

While theinvention has been described with particular reference to oneembodiment, it is to be understood that the scope of the invention isnot limited to the particular features illustrated and described, norotherwise than by the terms of the following claims.

I claim:

1. In a downdraft carburetor, a body section forming an inductionpassage and having a venturi and a fuel reservoir formed integraltherewith, a boss projecting from said body section into said fuelreservoir to a point adjacent the bottom thereof but separated from thewalls of the fuel reservoir by an annular fuel-receiving space, aninclined passage in said has terminating at said venturi, a fuel nozzlein said passage, and a baflle extending longitudinally beneath the bosslongitudinally beneath the body section, an integral boss formed on theouter surface of said sleeve and extending into the fuel reservoir, aplurality of'heat dissipating flanges carried by said boss, a fuelnozzle in said boss connecting the fuel reservoir and the inductionpassage, and a baille extending longitudinally beneath the boss andterminating beyond the end thereof, to deflect vapor bubbles away fromthe entrance to said passage.

3. In a carburetor having an induction passage, a primary venturi, afuel reservoir, 2. fuel nozzle adapted to discharge into the primaryventuri and communicating with the fuel reservoir by means of a bossprojecting into the fuel reservoir, said boss having a plurality of heatdissipating fins thereon, and a bailie extending longitudinally beneaththe boss and terminating beyond the end thereof, to deflect vaporbubbles away from the entrance to said passage.

4. In a carburetor, a fuel chamber, a body member forming an inductionpassage, an integral boss formed on said body member and projecting forasubstantial distance to a point ad- Jacent the bottom of the chamber,said boss being spaced from the walls of the fuel chamber and providedwith a plurality of heat dissipating flns, an inclined fuel passage insaid boss terminating in said induction passage, and a baflle extendingboss and terminating beyond the end thereof, to deflect vapor bubblesaway from the entrance to saidpassage.

FRANK C. MOCK.

